In situ observation and range extension of the first discovered monoplacophoran Neopilina galatheae

Monoplacophoran molluscs have been dubbed "living fossils" due to their absence in the fossil record for about 375 million years, until Neopilina galatheae Lemche, 1957 was trawled off Costa Rica in 1952. Since then, over 35 species of living monoplacophorans have been discovered. Nevertheless, in situ observations of these rare deep-sea animals remain scant. Here, we observed and collected an intact specimen of N. galatheae using a remotely operated vehicle from 2460 m deep on the Eastern Galapagos Spreading Center. The animal was found attached to the glassy surface of solidified basalt lava flow, and no feeding trails were found near the animal. Such hard substrate is in contrast with previous records that were trawled on sand and mud, suggesting Neopilina can be found on a wide range of substrates. This is the first time this species was collected since 1959, and represents a southeast range extension of about 1000 km for the species.